In some situations it is required to pick up soil at one location and transport it to another. In the case of road building for instance, the contour of the ground is changed to form a road by taking the soil from one location and placing it in another. Not only must the soil be removed from one location, it must also be placed in another specific location.
In many situations however, it is only desired to remove the soil from its current location, and the location it is moved to is not critical. Often it is desired to simply spread the removed soil so that it does not interfere with future operations on the land. An example is where ditches are made to drain standing water from ponds on agricultural lands.
Conventional soil moving machines include scrapers and loaders, where a generally horizontal blade is moved at a shallow depth along the ground, lifting soil and moving same into a bucket where it remains until dumped. Scrapers may incorporate a chain elevator to assist in moving the soil into the bucket. Trenchers or ditchers generally move the soil from the trench and pile it beside the trench, although ditchers are also known which spread the soil that is removed. Such soil-spreading ditchers are disclosed in U.S. Pat. Nos. 3,624,826 to Rogers, U.S. Pat. No. 5,237,761 to Nadeau et al., U.S. Pat. No. 5,113,610 to Liebrecht et al., and U.S. Pat. No. 6,226,903B1 to Erickson.
The soil moving machines of the prior art generally include a rotating impeller disc in which impeller blades on the disc which rotate with the disc can be subject to considerable damage if impacting rocks and other similar debris. U.S. Pat. No. 5,237,761 by Nadeau discloses the use of shear pins for fastening the blades to the disc to minimize damage to the blade upon impact with a rock, by allowing the blade to swing freely from a remaining fastener once the shear pin is broken. The blade is not functional however until the shear pin is replaced. Furthermore, the blade swings about a remaining fastener which is parallel to the disc axis of rotation such that the swinging blade can potential cause further damage to other elements of the implement. The orientation of the pivot axis of the blade also causes the blade body to bite into the main disc body in a twisting motion that may interfere with proper shearing of the shear pin causing unnecessary damage to the blade in some instance.
In other prior art soil-spreading ditchers, the blade must be replaced in its entirety subsequent to impact with a large rock or other similar debris.